[Lisa~]

The reps are so low (6 in stage 3, and then 4 in stage 5) that I think we've got to increase the weight proportionately. I read the "light" comment in the exercise description to mean light relative to your standard bilateral deadlift. Even though this is a deadlift, you can't use nearly as much weight as you can when you're standing on two feet.

How much weight is appropriate is determined by an individual's ability to execute the exercise with good form. For the single-leg RDL, I'd look for the ability to return to standing under control. If you can control your balance, especially during the concentric contraction of the working glutes, then the load is not too heavy.